Gymnosporangium Haraeanum SYD. is one of the oriental species of pear rust fungi and passes its life-cycle developing O and I on the Japan pear and III on the Juniper-tree (Juniperus chinensis and J. chinensis var. procumbens).
In the later stage of the pear rust disease we, not infrequently, observe the occurrence of natural infections wholly devoid of aecia. Following study was made to find out how such things happen and to clarify the sexual behaviour in the fungus.
Numerous monosporidial infections were obtained by sowing the sporidia sparsely on the pear leaves. Every monosporidial infection formed spermogonia, which excreated spermatia-containing nectar. At the end of about eleven weeks after inoculation, a large majority of such infections remained sterile, i. e. failed to produce aeciospores when they were kept in isolated condition; while the better part of those infections to which nectar containing spermatia had been transferred from several of the other infections began to develop aecia within about sixteen days after the treatment and then they behaved themselves normally in the course of the production of aeciospores. When a few monosporidial infections occurred close together, mixing of nectar resulted from coalescence of them and in such cases also aecia were produced in high percentage. Filtered spermogonial nectar which was free from spermatia had no such function as to induce the formation of aecia. Thus, the spermatia of the fungus have a role of supplying to the mycelia of monosporidial infections the opposite sex element. The fungus is heterothallic in a broad sense.

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When the cotton seedlings were artificially inoculated with Rhizoctonia solàni in the Petri dish, the invading hyphae progressed along the slightly depressed seam of the epidermis of root, hypocotyl, and cotyledon. The depression was increased as the fungus hyphae became closely attached.
Root tips were very susceptible to the attack of the fungus. The fungus penetrated the epidermis and branched out into the underlying tissues inter- and intracellularly extending even into the region within the endodermis. Infection in the root also occurred through the natural injuries as new secondary rootlets pushed out from the tap root.
Infection in the hypocotyl occurred mainly by means of ‘infection cushion’, and very rarely was it effected by simple strands of fungus mycelium.
Cotyledons were penetrated. both through the cuticle and the stomatal openings. Both types of infections occurred in about equal frequency in the upper surface of the cotyledon; but stomatal infection predominated in the lower surface.

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The writer reported already the results of his investigation on the histological changes of hypertrophied buds of the Camellia (Camellia japonica L.) caused by Exobasidium Camelliae SHIRAI. In the vicinity of Kyoto, the same plants are attacked very often by a different fungus belonging to the same genus, which is treated by HARA under the name of E. Camelliae SHIRAI var. nudo SHIRAI. The disease under consideration attacks the young leaves causing the circular spots as in the case of the blister blight of tea plant caused by E. vexans. The disease spreads sometimes to the petioles and also attacks the young green stems. The present paper deals with the results of the writer's investigation on the histological changes of deformed leaves, petioles and stems caused by this disease. Differing from the results of previous investigation on the hypertrophied buds, the deformation in the present disease seems to be occurred by hypertrophy of the cells only. Hyperplasia do not take place in all the affected parts and consequently the number of the layers of cells is not changed. The arrangement of the hypertrophied cells is regarded clearly as to be osmomorphosis. The hymenium of the causal fungus, having apparently exogenous appearance, develops at first under the epidermal cells or in the intercellular spaces of one to three subepidermal layers of cells. These overlying layers of cells rupture later, exposing the hymenium.

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The mycelial development of Piricularia Oryzae CAV. is generally poor in òrdinary synthetic nutrient solutions. The authors carried out cultural experiments of this fungus with several synthetic nutrient solutions in an attempt to set up a formula of somewhat more suitable one for the culture of the present fungus. Based upon the results obtained in the cultural experiments the authors contrived the following formula of a synthetic nutrient solution:
Potassium nitrate (KNO₃) 2.0g
Monopotassium phosphate (KH₂PO₄) 0.5g
Dipotassium phosphate (K₂HPO₄) 0.5g
Magnesium sulphate (MgSO₄·7H₂O) 0.5g
Calcium chloride (CaCl₂) 0.1g
Ferric chloride (FeCl₃) trace§
Sucrose 30.0g
Redistilled water 1000.0cc
§ One drop of 5% FeCl₃ solution for 30cc of the nutrient solution.
Hydrogen ion concentration of the present solution was about pH 6.3, and a slight precipitation unavoidably took place. The fungus grew tolerably well in this nutrient solution, and a grayish olive colored mycelial colony developed in 30 cc of this solution by a culture in a thermostat at 28°C for 30 days was measured to be more than 4 mg in dry weight. The present formula would be recommended as a suitable synthetic nutrient solution for the mycelial development of Piricularia Oryzae CAV.

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In field observations it has been noted that the rice blast disease outbreaks severely after the stormy weather. To study this connection experimentally, the present work was carried out. Rice plants were exposed to an artificial strong wind for several hours, and then the blast fungus, Piricularia oryzae CAV., was inoculated to them. As the results of the experiments, a marked increase of the infection was observed on the treated plants.
This may be attributed mainly to the facilitated infection occurred through the wounds produced on the foliage leaves due to the mutual rubbing or fluttering in the strong wind. Furthermore some physiological disorders of the host plant brought. about by remarkable dryness or mechanical injury of the leaves induced by the wind, were noted also as the possible factors lowering the resistance against the attacks of the present fungus.

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The present report dwelt upon the observations on downy mildew of wheat and its causal fungus, Phytophthora macrospora.
As for the causal fungus, only the oospore had been known until TASUGI discovered for the first time its conidial stage on rice in 1927. He reported in detail the morphological character of the fungus in 1930, and he stated that the causal organism should be transfered to Nozemia from Sclerospora.
The author happened to find the conidial stage of the fungus on wheat-plants badly affected by the downy mildew after a flood at Ikeda, Prov. Tokachi, Hokkaido in 1937. The conidia produced on wheat leaves in the fields were 57.5-97.5μ in length and 30.0-65.0μ in width; average 74.6×46.8μ. When these leaves were soaked in water, the spores elongated to 65.0-112.5×32.5-55.0μ; average 87.37×43.75μ. The latter measurements were correspondent to those reported by TASUGI about the conidia discovered on affected rice plants. Oogonia formed in the tissues of affected wheat were 55.0-100.0×50.0-95.0μ; mostly 62.5-75.0×56.5-72.5μ; average 69.12×65.13μ. Antheridia paragynous, 22.5-41.25×12.5-22.5μ; average 27.75×15.15μ. Oospores, . 42.5-72.5×42.5-70.0μ; average 60.25×56.67μ. Zoospores 12.5-16.25×10.0-12.5μ; average 14.17×10.8μ. The conidia were produced abundantly at 11°-24°C.
According to the morphological characteristics of the conidia it was concluded that the causal organism undoubtedly belongs to Phytophthora. Having compared the conidia and oospores formed on wheat and rice with those on other affected cereal crops and wild grasses, the author came to the conclusion that Sclerospora macrospora SACC., S. Kriegeriana P. MAGN, , S. Oryzae BRIZI are one and the same species.
Hereby the author propose to change the nomenclature of the causal organism as follows:
Phytophthora macrospora (SACC.) S. ITO et I. TANAKA n. comb.
=Sclerospora macrospora SACC. Hedw. XXIX, 155, 1890: Syll. Fung. IX, 342, 1891-BERL. Monogr. Peronosp. 148, 1903.
=Sclerospora Kriegeriana P. MAGN. Verh. Ges. Deutsch. Nat. u. Aerzte, 67; Vers. zu Lübeck, 1895, 100-SACC. et SYD. in SACC. Syll. Fung. XIV, 461, 1899.
=Sclerospora Oryzae BRIZI, La Peronospora del Riss, in Nature, X, 168, 1919-TROTT. in SACC. Syll. Fung. XXIV, 65, 1926.

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[in Japanese]

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(1) The present paper deals with the study carried out by the writers on a new fungus which causes an anthracnose disease of jute.
(2) The jute anthracnose affects the stems, leaves and pods of this crop and its presence in Kumamoto and Shizuoka Prefecture was first observed in 1938. In the next year it has been found in Aichi Prefecture.
(3) The causal organism has been isolated and its pathogenicity has been proved by inoculation experiments. The incubation period is about three days.
(4) As the fungus seems to be new to science, the name Colletotrichum Corchorum is proposed and a brief technical description is given, as follows:
Colletotrichum Corchorum IKATA et TANAKA nov. sp.
Lesions on stems, leaves and pods, brown to black, not sunken, definite in outline. Acervuli black, superficial, scattered; stroma patelliform, 100-350μ in diameter by 25-50μ high; setae several to abundant, originating from margin of stroma, yellowish brown to black and becoming lighter toward the apex, 2 to 5 septate, 36-117 μ long by 3.6-5.0 μ wide. Conidiophores simple, hyaline, arising from stroma, 15-35 μ long by 3-4 μ wide; conidia abundant, non-septate, hyaline, curved, bluntly tapered, oblong-fusoid to falcate-fusoid, 12-25×3.6-6.0μ, with 16-22×4μ as the most common size.
HAB: Parasitic on stems, pods and leaves of Corchorus capsularis L.
(5) The optimum temperature for growth of the fungus is 30°C.
(6) The disease is seed-borne, the fungus mycelium exists in the seed and spores are adhering on the external part of seeds.

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[in Japanese]

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1. The present paper deals with a method of disease resistance trials of sugar cane varieties to red rot caused by Colletotrichuin falcatum WENT and with the results hitherto obtained by this method at the Government Sugar Experiment Station, Tainan, Formosa.
2. The sugar cane varieties improved in our station and other imported ones are tested for the resistance to red rot by inoculating the causal fungus to the stalks of the growing canes.
3. The main points of the method of inoculation and measurement of the size of affected part of the stalks are as follows:
(1) The fungus cultured at 28°C for four days on cane juice agar is used for the inoculum.
(2) A small portion of the fungus culture is inserted into the hole, bored by a kind of punch with an opening 7 mm in diameter, in the center of the internode of the cane stalk.
(3) The inoculated stalks are split lengthwise at the harvest time and the size of the affected tissues is measured.
(4) The inoculation is performed at the time two to three months prior to the harvest.
(5) About thirty to fourty stalks of each varieties may be sufficient for one trial.
4. The resistance of each variety to red rot is judged by the theoretical figure derived from the number of the diseased internodes. When the area of the affected portion of the inoculated stalks holds more than 2/3 part of an internode, it is collected under sign + + +, between 2/3 and 1/3, it is collected under sign + +, and below 1/3 under sign + respectively. The number of diseased internodes belonging to the class + + + is then multiplied by 3/3, the number of the class + + by 2/3, and the number of the class + by 1/3. The degree of damage (b) will be obtained when total sum of the figure of three classes of each variety is divided by the number of stalks measured. Then the ratio (b'), quotient of the figure of damage of each variety by that of the standard one, may be the theoretical figure to compare the resistance of each variety. If the figure of ratio (b') of one variety is above 1 the variety may be less resistant than the standard one, on the contrary, if the figure of ratio of another variety is below 1, the variety may be more resistant than the standard one.
5. The varietal resistance of sugar cane to red rot obtained by this method are tabulated elsewhere, which has been carried out since 1936.
6. For the selection of the resistant varieties of sugar cane to red rot this inoculation technique together with the field observation are now put in practice at our station.
Government Sugar Experiment Station,
Tainan, Formosa

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The present investigation was performed cytologically in order to find any difference in the reaction of the rust of Acacia confusa to host cells at different parts of the same phyllode as well as to those of different phyllodes with different maturity.
(1) Susceptible region, viz., young, growing portion of the phyllode.
(a) The entering hyphae produced from appressoria usually invade through stomatal apertures, less frequently piercing cuticle directly (fig. 3), and form a substomatal vesicle (fig. 1, 2), from which haustoria are produced in the adjacent cells. After a while a few primary hyphae are also formed from the vesicle, making their way down through palisade parenchyma to spongy tissues, but never inserting haustoria into the palisade cells, or very rarely, if any. On the other hand, the development of the fungus is mostly achieved in the spongy tissue, producing many haustoria until the time of teliospore-formation which usually takes place after about 4-5 weeks. In any cases studied noncompatibility between host and parasite can not be clearly demonstrated.
(b) The plastids of the palisade cells in close contact with the invading hyphae as well as those of several cells near the hyphae first reduce in size and function, but after the actual invasion of haustoria these degenerated plastids recover in size, and also seem to become more active in function than ever. In the case of the spongy tissue, the plastids of the cells become larger and more greenish in color, and increase in number when actually invaded by the haustoria. Moreover, starch grains are found more numerous in the invaded cells. The starch grains present in the invaded palisade and sponge cells are different in form, viz., simple (fig. 10) and compound (fig. 11), respectively.
(c) The affected cells are not hyperplasied in any noticeable degree, but more or less hypertrophied (fig. 8).
(d) The haustorium has a slender neck at its base, and generally small and simple, though some digitate haustoria (fig. 13, 11) are usually found in the cells surrounding the substomatal cavities. The haustorium is as a rule incased in a thick wall and dead when old (fig. 15, 16).
(2) Immune region, viz., very young, rapidly growing portion of the phyllode.
In this developing stage of phyllodes stomata have not yet been sufficiently developed, so that the parasite is unable to enter the host tissue except in the case of more advanced stage, in which the parasite is able to enter through stomatal apertures, though with much difficulty. The entering hypha produces the substomatal vesicle in the same manner as stated above, but the parasite can not further develop at all and is soon perished (fig. 5, 6) as a result of the toxic secretion from the host cells (cf. 8). In rare cases, however, the fungus can develop in a few days and produce some rudimentary haustoria, but it never continues to grow any further and is finally perished (fig. 18) prior to the death of the host cells, though there are found several cases where it is impossible to determine which is first deceased. On the other hand, the guard cells beneath the appressoria and the epidermal cells connecting with the former are very frequently killed (fig. 4) though this occurs less frequently in the advanced stage of host development, it is presumed that the parasite may also secrete some toxic substance, to which the host cells are more sensitive when they are younger.
(3) Immune region, viz., mature, fully grown portion of the phyllode.
The parasite is able to enter the host through stomatal apertures with ease, and produces the substomatal vesicle as usual, provided that the urediospores can germinate and produce appressoria (in nature, as has already been stated in a previous paper, the urediospores can hardly germinate, or none, on such a portion).

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1. In this paper describes the results of studies on the effects of hydrogen-ion concentration in the juices of the stems and leaves of the Udo salad plant and in the plants belonging to the genus Aralia on the development of the atrophic fire-blight disease in the Udo salad plant (Aralia cordata THUNB.) causing Phoma Araliae COOKE et MASSEE var. microspora WATANABE.
2. The extent of hydrogen-ion concentration in the juices of the stems and leaves of the Udo salad plant and in plants belonging to the genus Aralia seems to have no particular effect on the development of the present disease.
3. In the development of the present disease, no special relation could be recognized between the extent of the hydrogen-ion concentration in the juices of the stems and leaves of the Udo salad plant and in the plants belonging to the genus Aralia and the extent of hydrogen-ion concentration on the growth of mycelia and germ-tubes from the pycnospores of the causal fungus.
4. From the above mentioned results, the agronomic or regional varieties and strains of “Kan-Udo” were susceptible as well as the agronomic or regional varieties and strains of “Haru-Udo” were most resistant to the present disease, such results are impossible depend upon the hydrogen-ion concentration of the stems and leaves of the host plant.

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The writer has already reported that, in the seed-bed of rice in tidal paddy-field of Tyosen where sulphate-reducing bacteria, Microspira desulfuricans (BEIJERINCK) van DELDEN, took an active and vigorous part, and that the rotting of rice-seeds and seedlings prevailed as the consequence of a great lack of oxygen.
This paper reports that injury in the same manner occurs also in common paddy-fields.
The injured soils investigated by the writer contain much of organic matters in addition to stagnation of water, and the reaction of soil is weak alkaline (pH 7.17.3). The symptom appears on germ elongated to 13 cm of cotyledon as a germ with curvature and check of the elongation of the first leaf, which becomes dead and rots with age, and the growth of its root is checked, and then withers with a black colouration of the precipitation of iron sulphite.
In the injured soils, sulfate-reduction is very visible, and sulfate-reducing bacteria and the specially associated organisms have been isolated. Those bacteria are found to be identical with Microspira desulfuricans (BEIJERINCK) van DELDEN, and Pseudomonas sp. respectively which had been isolated by the writer from tidal paddy-fields, after comparing their morphological, cultuarl, and physiological characters.
From the results of experiments, these injurious soil conditions are not only closely resembles to those of tidal paddy-fields, but they are also similar to the conditions produced by the inoculation of sulfate-reducing bacteria, Microspira desulfuricans (BEIJERINCK) van DELDEN, in sterilized soil.

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1. On inoculating 24 species (13 families) of Phanerogams with the conidia of Peronospora Aparines (de BARY) GÄUM. penetrations are obtained in 10 species (6 families) among them.
2. Penetration occurs through the boundary line of the epidermal cells on the under surface of the leaf, but on several plants also stomatal penetration or direct penetration of the epidermal cell wall is rarely observed.
3. The germ tube of the conidium usually forms the appressorium on the boundary line of the epidermal cells, and the infection hypha passing through intercellularly, sends out haustorium into the epidermal cell on the host but not on other plants.
4. Also on the unpenetrated plants the germ tube of the conidium is observed usually to form appressorium on the boundary line of the epidermal cells.
5. According to the point of penetration none or one to all of the epidermal cells with which the infection hypha comes in contact show granulations or disorganizations of protoplasms on the host as well as on other plants.
6. On several plants of penetrated and unpenetrated, so-called callus is formed reacting the attack of the fungus.

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The present paper deals with two species of Alternaria injurious to cotton fibres in nearly ripe balls, found in last season in western Japan. One of them attacks cotton leaves, balls and cotton fibres in balls, and the other mostly cotton fibres. According to the characters of the both fungi, the former species can be referred to A. macrospora ZIMMERMAN and the latter may possibly be A. gossipii (JACZ.)
Cotton fibres in balls in various degrees of maturity, commercial cotton and absorbent cotton were inoculated with the pure cultures of the Alternaria under consideration. With the exception of the absorbent cotton, discoloration or blackening of the cotton fibres inoculated was observed.
The relation of temperature and hydrogen ion concentration to the growth of the both species was studied. It was found that the minimum; optimum and maximum temperatures for the mycelial growth of the both fungi were same and about 5°, 27-30° and 36°C., respectively. The acid limit for the mycelial growth of the both fungi was about pH 2, the alkaline limit seemed to be slightly above pH 10. The optimum hydrogen ion concentration for the growth was about pH 5.

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Trichoderma viride (Trichoderma lignorum) is found to be a beneficial fungus parasitizing the sclerotia and mycelia of sclerotial fungi and often doing to death. The fungus is, on the other hand, a weak parasite to sweet potatoes and also a harmful one to depress the growth of various crops, but the detrimental effect is rather greater on pathogenic fungi than on crops. It seems to be quite hopeful to use Trichoderma as an agent for controlling biologically sclerotial diseases and other fungous ones.

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1. A white mosaic of tobacco was found in tobacco growing district near Hukuoka, which is different from JOHNSON's “white mosaic”.
2. This virus is infectious to most species of solanaceous plants, but no infection occurs on cucurbitaceous plants.
3. In general, the virulence of the virus is not so destructive, but petunia is retarded its growth severely.
4. Mottlings are produced when Nicotiana sylvestris is inoculated with the virus.
5. The present virus may be a strain of tobacco common mosaic virus (Nicotiana virus 1) which causes white mottlings on tobacco.

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Four different spores of a sooty mould, including ascospore, pycnospores and conidium, appear to be associated with the scale Tachardina theae GREEN & MANN on the same leaf of persimmon in Formosa. The results of the studies made on the cultures originated from single spore isolations show that these isolates can be separated into four distinct, species, i. e. the genera Phaeosaccardinula, Triposporium, Microxyphium and Capnodium. Among them the first one which is characterized by a brownish sooty appearance is very prevalent, covering the greater part or the whole of the leaf surface, not infrequently contaminated by the remaining three moulds.
The general character of this brownish sooty mould is as follows:
Colonies epiphyllous, diffuse, brownish black to dark brown, glabrous, rather thin. Perithecia subglobose or depressed globose, glabrous, indistinctly ostiolate, black, 168-266μ in diameter. Asci ellipsoid, obovoid or clavate, thickened apex, 4-8-spored, 57-87×21-37μ. Ascospores long ellipsoid, long obovoid or cylindric, round or obtuse at the ends, transversally 3-9-septate, longitudinally 2-8-septate, hyaline to dilute brown, 23-46×8-14 μ.
As regards the host range it has been confirmed, so far as the present studies are concerned, that the fungus under consideration occurrs on 23 different species of plants belonging to 16 families, the insects associated with the mould being the following six species, including Tachardina theae, Pulvinaria psidii, Pinnaspis aspidistrae, Thoracaphis fici, Phyllaphoides bambusicola and Trichoregma minuta. (Table 3).
The brownish sooty mould may be identical with Limacinula javanica (ZIMM.) HÖHNEL, but HÖHNEL, THEISSEN and SYDOW made the genus Limacinula a synonym of the genus Phaeosaccardinula. Therefore, the present author proposes a new combination, viz. Phaeosaccardinula javanica (ZIMM.) comb. nov., for this fungus. The following four species: Phaeosaccardinula citrivola HARA on Citrus spp., Zukaliopsis Gardeniae SAWADA on Gardenia florida, Phaeosaccardinula samoensis HÖHNEL and Phaeosaccardinula Theae (SYD. & BUTL.) THEISS. & SYD. are considered to be identical with the present fungus.

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[in Japanese]

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1. In 1936 a new leaf disease of Camellia japonica var. spontanea was found in the Tokyo Imperial University Forest, Kiyosumi, Awa; and its symptom, etiology, pathology and distribution were studied.
2. On the upper surface of the leaf, there first appear minute discolored specks, which gradually enlarge to circular spots, 2-4 mm in diameter. The spots, having indistinct margins, are at first pale green and become later greenish white. Turning black in the centers, the spots assume “snakeeye” form.
3. The disease is caused by a parasitic fungus. It invades through the stoma on the under surface of the leaf into the mesophyll, and forms its stroma in the respiratory cavity. The invaded tissues perish and turn brown, while the cells surrounding them undergo division. The stroma, breaking the overlying epidermis, is exposed as a conical protuberance, measuring 1 mm in diameter and 0.5 mm high. On the stroma, many synnemata are developed, measuring 70×850μ, producing conidia in Penicillium type. The conidia are hyaline, ovoid or ellipsoid, and catenate, measuring 6.0-10.6×3.5-4.5μ.
4. The “leaf spot” is proposed as the name of the disease and the causal fungus is described under the name of Graphiothecium Kusanoi sp. nov.

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I. Damping-off of China aster (Callistephus chinensis).
Seedlings are infected. The diseased part becomes brown, with water-soaked appearance, resulting in the damping-off. Though the causal fungus is a pythiaceous one closely related to Pythium megalacanthum, it differs from the latter in the production of conidia, absence of sporangia and the size of oospores. Therefore, the writers propose to give it a new name, Pythium megalacanthum var. Callistephi which may be described as follows: -
Mycelium hyaline, well developed in host tissue and in culture. Hyphae branched, 2.8-6.4μ in diameter, often septate in old culture. Conidia usually terminal and rarely intercalarly, hyaline and sphaerical, 23.1-44.4μ (av. 34.5μ) in diameter, germinating directly. Oogonia terminal, hyaline, sphaerical, usually covered with many spines (5.6-8.3×2.8-4.6μ), without spines 32.4-50.9μ (av. 41.6μ) in diameter. Antheridia terminal or intercalarly, hyaline, kidney-shaped, 11.1-21.3×8.3-17.6μ (av. 15.7×12.6μ), usually one, rarely two to an oogonium. Oospores sphaerical, almost filling the oogonium, 22.2-39.8μ(av. 33.1μ) in diameter, wall light yellowish brown, smooth, 0.9-2.8μ in thickness. Parasitic on Callistephus chinensis NEES.
The fungus grows well on oatmeal and potato agar. The range of the temperature of its growth lies between about 10°C and 29°C and the optimum 23°C. The most favorable pH of the medium for its growth seems to be pH 5.8-6.9.
In inoculation experiments, the seedlings of Callistephus chinensis, Lactuca sativa and Papaver Rhoes are severely infected, resulting in the typical damping-off. Zinnia elegans is somewhat less susceptible than the above-mentioned plants. Calendula officinalis and Antirrhinum majus are weakly attacked and Solanum Lycopersicum reveals only the root-browning symptom. No sign of infection is seen on Solanum melonga and Cucumis sativus.
II. Damping-off of Zinnia (Zinnia elegans.)
Seedlings are also infected, diseased parts becoming brown and damping-off as in the case of China aster. A pythiaceous fungus is easily isolated from the diseased part.
The fungous growth is best on potato agar, and well also on bean agar. On the other media it grows feebly or not at all. The optimum temperature for its growth seems to be about 24°C, the minimum and the maximum being 8°C and 35°C respectively. The optimum pH of the medium for its growth lies between pH 5.8 and 6.5.
In inoculation experiments, it attacks most severely the seedlings of Zinnia elegans and Callistephus chinensis, Brassica oleracea, Platycodon glaucum and Lactuca sativa, Antirrhinum majus, Calendula officinalis and Papaver Rhoes are also severely infected. Cucumis sativus, Solanum Lycopersicum and S. melonga are weakly attacked. No infection is observed in Pisum sativum.
Compared to several species of the genus Pythium where oogonia are covered with spines, it is closely related to Pythium spinosum, in morphological and physiological respects. But they differ somewhat in the pathogenicity and the size of conidia. So, the writers consider that their fungus is a strain of P. spinosum.

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